On-site charging of cooling systems such as air conditioners, freezers, and refrigerators is problematic in cold weather because the refrigerant cools to the point where it is difficult to sustain a vapor charging pressure. Furthermore, vaporization of the refrigerant causes atmospheric humidity to freeze on the outside of the refrigerant container.
There are many known techniques for facilitating the transfer of refrigerant from a charging cylinder to the unit requiring charging. For example, U.S. Pat. No. 5,377,495, issued to Daigle, discloses a refrigerant transfer system utilizing a temperature controlled thermal jacket for selectively heating and cooling a refrigerant cylinder, the thermal jacket being controlled by an electronic motor, a thermostat, a temperature probe, and a high temperature cut out. U.S. Pat. No. 5,249,434, issued to Abraham, discloses a device for automatically charging refrigeration systems having a vessel for holding refrigerant containers, a digital controller, a pressure sensor for providing readings to the digital controller, control software, several controls and detection devices for opening and closing valves and detecting errors, and a means for pressurizing the refrigerant by heating the vessel. U.S. Pat. No. 4,539,817 issued to Staggs, U.S. Pat. No. 4,766,733 issued to Scuderi, U.S. Pat. No. 5,406,806 issued to Ricketts, U.S. Pat. No. 3,903,709 issued to Anderson, and U.S. Pat. No. 4,982,576 issued to Proctor all disclose refrigerant charging systems utilizing complex means for storing and heating the refrigerant, as well as complex controls and regulators.
The prior art refrigerant charging systems have the disadvantages of being costly, complicated, and difficult to transport for on-site charging. There is an explicit need for an inexpensive, easily portable unit for charging refrigerant systems.